Firstborn girls are statistically more likely to run the world

There's a hunger in psychology for birth-order effects — prophecies about personality that originate in whether your siblings are older or younger than you. Alfred Adler, a student of Freud, pioneered the idea that firstborns seek out leadership roles, delight in rules and order, and value achievement; that lastborns tend to be charming, popular and spoiled; that middle children — yawn, who cares? — and that onlies can be both mature and dependent.

But many of the studies trying to back up these truisms with evidence use shoddy methodology that either fails to control for family size, economic status or parents' educational attainment or extrapolates about dynamics within a family from comparisons between families.

New research from scientists at the University of Essex, though, uses multilevel modeling techniques to overcome these hurdles, and the results suggest that birth-order effects are more than just a methodological illusion. At least when it comes to academic achievement, the mythical yeti of family psych has been bagged and examined — call your older sister!

Feifei Bu looked at more than 1,503 sibling clusters and 3,532 individuals taking part in the massive British Household Panel Survey, which has been parsing the isle's domestic DNA since 1991, and its successor, the Great Britain Household Longitudinal Study. She finds that firstborns are more likely to be the "ambitious" and "accomplished" ones in their families. Firstborn girls especially outdo their siblings in educational dreams and attainment — they are 13 percent likelier to aspire to graduate school than firstborn boys.

On the other hand, the researchers write, "We see no evidence that the sex of one's siblings has any effect on educational aspiration or outcomes. Nor do we find a strong relationship between sibship size and either educational aspiration or attainment."

What does seem meaningful is the time spacing between children: Eldest kids separated from their brothers and sisters by a significant age gap — four or more years — are likelier, at 13, to express an interest in higher education, and they go on to pursue more advanced degrees.